Sampling device



Jan. 17, 1967 w. L. THOMAS SAMPLING DEVICE Filed April 1, 1964 INVENT'OR WILLIAM LLEWELYN THOMAS MORGAN, FINNEGAN, DURHAM a PINE ATTORNEYS United States Patent 3,298,236 SAMPLHNG DEVICE William Llewelyn Thomas, Sunbury=on-Thames, Middlesex, England, assignor to The British Petroleum Company Limited, London, England, a corporation of Great Britain Filed Apr. 1, 1964, Ser. No. 356,456 Claims priority, application Great Britain, Apr. 10, 1963, 14,329/63 3 Claims. (Cl. 73-425.6)

This invention relates to sampling devices for withdrawing samples of fluid from, or introducing samples of fluid into, apparatus operating under a high degree of vacuum or at a high pressure.

At the present time if samples are required to be taken from, or introduced into, apparatus operating under a high degree of vacuum, or at a high pressure, it is necessary to have a complicated by-pass system including a number of valves.

It has been found that such samples can be withdrawn or introduced, even under the above-mentioned conditions, via a rubber septum or serum cap on the apparatus.

According to the present invention we provide a sampling device capable of withdrawing samples of fluid from, or introducing samples of fluid into, apparatus operating under a high degree of vacuum or at a high pressure, comprising .a hypodermic syringe including a piston having an O-ring seal located in a groove around the periphery of the piston in a plane normal to the longitudinal axis of the piston.

The term high degree of vacuum where used in this specification is intended to mean a vacuum within the range 760 to 1(lmilimetres of mercury.

The term high pressure where used in this specification is intended to mean a pressure at least as high as 50 p.s.1.g.

In order that the invention can be more clearly understood a specific embodiment thereof will hereinafter be described, by way of example only, with reference to the accompanying drawing which shows a sectional view of a sampling device used in conjunction with an apparatus containing fluid to be sampled.

Referring now to the drawing, there is shown a container 11 in which is contained a fluid 12. A pipe 13 is welded through an aperture in the wall of the container 11, the free end of the pipe 13 being sealed with a serum cap 14.

A sampling device 15 comprising a hypodermic syringe is shown in the sampling position with its needle 16 inserted into the serum cap 14. The sampling device 15 comprises barrel 17, into one end of which the needle 16 is located. The other end of barrel 17 is externally threaded to receive a screw cap 18, the latter having an internally threaded portion Which co-operates with .a threaded rod 19. A piston 20 is attached to one end of the threaded rod 19 and a handle 21 is fixed to the other end. The piston 20 has an O-ring seal 22 located in a groove around the periphery of the piston 20 in a plane normal to its longitudinal axis. The O-ring seal 22 ensures a fluid tight seal between the piston 20 and the barrel 17. The piston 20 is moved in either direction along the inside of barrel 17 by rotation of the handle 21 in the appropriate direction, a small diameter hole 23 being provided in screw cap 18 to allow air to flow into and out of the inside of barrel 17 behind the piston 22.

The sampling device 15 is used in the following manner. Screw cap 18 is screwed down tight onto the barrel 17 and the piston 20 is then moved down to the end of the barrel 17 to exclude as much air as possible by rotating handle 21 in a clockwise direction. The needle 16 is then inserted through the serum cap attached to the apparatus to be sampled and a sample of liquid is drawn into the barrel 17 by counter-clockwise rotation of handle 21. When suflicient sample has been collected the needle 16 is removed from the serum cap. The sample is then ejected from the barrel 17 as required by clockwise rotation of handle 21. 7

An experimental model of the sampling device as shown in FIGURE 1 has been made and tested. It was found that samples can be withdrawn from vacuum systems operating at pressures at least as low as 10" milimetres of mercury. Samples can also be withdrawn from systems operating at pressures above atmospheric at least as high as 50 p.s.i.g. It was also found that for withdrawing liquid samples from .a molecular still at a pressure of l() millimetres of mercury it was advantageous to use a needle having a bore of 0.003 inch diameter or more because of the small driving force which existed. Needles of such large gauge are not necessary for introducing samples into high vacuum systems nor are they necessary for withdrawing or introducing samples into apparatus at atmospheric or higher pressure or for use with gas samples at any pressure.

The sampling device is preferably fabricated from metal, the needle consisting of stainless steel hypodermic tubing. However it is possible to use other materials, for example the barrel may be constructed from glass if require-d.

In the arrangement shown in FIGURE 1 the piston shaft has been threaded, so that sample removal or sample introduction is effected by rotating the handle. This is not absolutely essential but it does have the advantage that it prevents the piston from being damaged by impact against the end of the barrel by sudden release of the handle under vacuum as might occur if the shaft is not threaded.

I claim:

1. A sampling device capable of withdrawing samples of fluid from, or introducing samples of fluid into, apparatus operating under a high degree of vacuum or at a high pressure, comprising a hypodermic syringe including a barrel, a needle of hypodermic tubing operatively secured to said barrel, a piston positioned within and having a diameter approximately equal to the bore of said barrel, said piston having a groove around its periphery in a plane normal to its longitudinal axis and an O-ring located in said groove sealing with said barrel, and a threaded member fixed to said piston, the arrangement being such that rotation of said threaded member relative to said barrel causes longitudinal movement of said piston within said barrel.

2. A sampling device capable of withdrawing samples of fluid from, or introducing samples of fluid into, apparatus operating under a high degree of vacuum or at a high pressure, comp-rising a hypodermic syringe including a barrel, a needle of hypodermic tubing having a bore of approximately 0.033 inch diameter operatively secured to said barrel, a piston positioned within and having a diameter approximately equal to the bore of said barrel, said piston having a groove around its periphery in a plane normal to its longitudinal axis and an Oring located in said groove sealing with said barrel.

3. A sampling device as claimed in claim 1 wherein the threaded member is rotatably mounted through a cap located at the end of the barrel remote from the needle.

References Cited by the: Examiner UNITED STATES PATENTS 1,556,085 10/1925 De Pew 1282l8 3,119,272 1/ 1964 I-Iaunschild 73425 .4 3,151,617 10/1964 Baum 128-218 LOUIS R. PRINCE, Primary Examiner.

S. C. SWISH'ER, Assistant Examiner. 

1. A SAMPLING DEVICE CAPABLE OF WITHDRAWING SAMPLES OF FLUID FROM, OR INTRODUCING SAMPLES OF FLUID INTO, APPARATUS OPERATING UNDER A HIGH DEGREE OF VACUUM OR AT A HIGH PRESSURE, COMPRISING A HYPODERMIC SYRINGE INCLUDING A BARREL, A NEEDLE OF HYPODERMIC TUBING OPERATIVELY SECURED TO SAID BARREL, A PISTON POSITIONED WITHIN AND HAVING A DIAMETER APPROXIMATELY EQUAL TO THE BORE OF SAID BARREL, SAID PISTON HAVING A GROOVE AROUND ITS PERIPHERY IN A PLANE NORMAL TO ITS LONGITUDINAL AXIS AND AN O-RING LOCATED IN SAID GROOVE SEALING WITH SAID BARREL, AND A THREADED MEMBER FIXED TO SAID PISTON, THE ARRANGEMENT BEING SUCH THAT ROTATION OF SAID THREADED MEMBER RELATIVE TO SAID BARREL CAUSES LONGITUDINAL MOVEMENT OF SAID PISTON WITHIN SAID BARREL. 